Tomato Tuna Casserole

All times are approximate, received this recipe from my mom, who received it from her father, who both passed this last year, only recipe I ever managed to get out of my mom before she died. As a family recipe all amounts are to our own tastes. :o) Childhood favorite of mine, and still a good comfort food. Freezes into separate meals well!

• Ready In: 55 mins
• Serves: 10-15

Ingredients

• 19 1⁄2 ounces  red pasta sauce (any flavor will do if you choose onion you can skip the onion)
• 1 (8 ounce) can tuna
• 2 (8 ounce) boxes  macaroni and cheese mix (preferably Kraft ^.^)
• 1⁄2 cup milk
• 1⁄2 cup butter
• 1  cup  diced onion
• 1  tablespoon butter (for caramelizing onions)

Directions

1. Prepare Mac n Cheese according to box instructions, EXCEPT cook noodles for half the recommended time.
2. Drain the canned tuna, Bring to simmer pasta sauce and add the tuna, As pasta sauce is simmering, caramelize the diced onion in a separate Pan (or caramelize the onions in the same pan, then do above step) making sure onion is very tender.
3. Add onion to Tuna Pasta Sauce (or vice versus), simmer for a few more minutes.
4. Transfer Pasta Sauce to the pot holding the macaroni and cheese, stir until mixed, then transfer to a large baking dish.
5. Bake at 350°F for 20 minutes to blend flavors and finish cooking the noodles.